1/*	$NetBSD: hash.h,v 1.5 2021/12/19 12:02:40 riastradh Exp $	*/
2
3/*-
4 * Copyright (c) 2013 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Taylor R. Campbell.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32#ifndef _LINUX_HASH_H_
33#define _LINUX_HASH_H_
34
35#include <sys/param.h>
36#include <machine/limits.h>
37
38static inline unsigned long
39hash_long(unsigned long value, unsigned int bits)
40{
41	const unsigned long factor = (sizeof(factor) > 4?
42	    0x9e37fffffffc0001ull : 0x9e370001ul);
43
44	return ((value * factor) >> ((CHAR_BIT * sizeof(value)) - bits));
45}
46
47static inline uint32_t
48hash_32(uint32_t value, unsigned int bits)
49{
50	return (value * 0x61c88647) >> (32 - bits);
51}
52
53static inline uint64_t
54hash_64(uint64_t value, unsigned int bits)
55{
56	return (value * 0x61c8864680b583ebull) >> (64 - bits);
57}
58
59#endif  /* _LINUX_HASH_H_ */
60